Dipeptidyl peptidase-IV (DPP-IV) inhibitors are a new generation of peroral drugs for treating type 2 diabetes and act by enhancing the activity of incretin, belonging to non-insulin therapeutical drugs. Compared to conventional drugs for treating diabetes, DPP-IV inhibitors have no adverse effects such as weight gain and edema etc.
The compound (R)-2-[[7-(3-aminopiperidin-1-yl)-3,5-dimethyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-1-yl]methyl]benzonitrile represented by formula (1) (hereinafter, referred as Compound A, which was described in the patent application CN201010291056.9) is a DPP-IV inhibitor compound, and has a strong inhibitory effect and a very high selectivity for DPP-IV.

In the research and development of medicines, the study on crystal forms is very important, and different crystal forms of a compound will result in different properties such as stability and solubility etc. Accordingly, after extensive investigation on the crystal forms of Compound A or salts thereof, the present inventors have found and identified crystal forms of a salt of Compound A.